<html>
<head>
<style>
div {
  position: absolute;
  width: 100px;
  height: 100px;
}
body {
  position: relative;
}

#one {
  top: 0;
  background-color: red;
  z-index: 3;
}

#two {
  left: 30px;
  top: 30px;
  background-color: blue;
  z-index: 2;
}

#three {
  left: 60px;
  top: 60px;
  background-color: green;
  z-index: 1;
}

#explain {
  top: 180px;
  width: 100%;
  height: auto;
}
</style>
</head>
<body>
 <div id="one"/>
 <div id="two"/>
 <div id="three"/>
 <div id="explain">You should see a red square on top of a blue square on top of a green square.</div>
</body>
</html>
